Methods and apparatus for facilitating negative feedback, providing loop stability, and improving amplifier efficiency

Abstract

An amplifier is described having an amplification stage in a first feedback loop. The amplification stage is operable to open the first feedback loop during operation of the amplifier. The amplifier further comprises a feed forward path bypassing the amplification stage. The feed forward path is operable to provide a second feedback loop when the first feedback loop is open.

What is claimed is:  
     
       1. An amplifier comprising an amplification stage in a first feedback loop, the amplification stage being operable to open the first feedback loop during operation of the amplifier, the amplifier further comprising a feed forward path bypassing the amplification stage, the feed forward path being operable to provide a second feedback loop when the first feedback loop is open. 
     
     
       2. The amplifier of  claim 1  further comprising a frequency selective network to operable to provide noise shaping in a frequency band of interest using negative feedback. 
     
     
       3. The amplifier of  claim 2  wherein the frequency selective network comprises at least one resonator stage. 
     
     
       4. The amplifier of  claim 2  wherein the frequency selective network comprises at least one integrator stage. 
     
     
       5. The amplifier of  claim 1  further comprising bias control circuitry for controlling a bias point associated with the amplification stage. 
     
     
       6. The amplifier of  claim 5  wherein the bias control circuitry comprises bias voltage control circuitry for controlling a bias voltage associated with the amplification stage, and bias current control circuitry for controlling a bias current associated with the amplification stage. 
     
     
       7. The amplifier of  claim 6  wherein the bias voltage control circuitry is operable to set the bias voltage at one of a plurality of bias voltage values, and wherein the bias current control circuitry is operable to set the bias current at one of a plurality of bias current values. 
     
     
       8. The amplifier of  claim 5  wherein the bias control circuitry is operable to control the bias point in response to any of an input signal level, power control information received from a remote device, and battery charge information. 
     
     
       9. The amplifier of  claim 1  wherein the amplification stage comprises a single transistor and an inductor which are operable to alternately conduct load current. 
     
     
       10. The amplifier of  claim 1  wherein the amplification stage at least one switching device. 
     
     
       11. The amplifier of  claim 10  wherein the at least one switching device comprises any of a field-effect transistor, a bipolar junction transistor, and a vacuum tube. 
     
     
       12. The amplifier of  claim 1  wherein the amplification stage is characterized by operation in one of classes B, AB, C, D, E, F, G, and H. 
     
     
       13. The amplifier of  claim 1  having a frequency band of interest associated therewith. 
     
     
       14. The amplifier of  claim 13  wherein the frequency band of interest is the radio frequency (RF) band. 
     
     
       15. The amplifier of  claim 13  wherein the frequency band of interest is the base band. 
     
     
       16. The amplifier of  claim 1  wherein the first and second feedback loops comprise feedback circuitry. 
     
     
       17. The amplifier of  claim 16  wherein the feedback circuitry comprises a plurality of passive circuit components. 
     
     
       18. The amplifier of  claim 16  wherein the feedback circuitry comprises a combination of active and passive components. 
     
     
       19. The amplifier of  claim 1  wherein the feed forward path comprises at least one passive circuit component. 
     
     
       20. The amplifier of  claim 1  wherein the feed forward path comprises at least one active component. 
     
     
       21. The amplifier of  claim 20  wherein the at least one active component comprises one of a common-emitter transistor and a common-source transistor coupled between an output and an input of the amplification stage. 
     
     
       22. An electronic system comprising the amplifier of  claim 1 . 
     
     
       23. The electronic system of  claim 22  wherein the electronic system comprises one of a mobile wireless communication device and a wireless base station in a wireless communication network. 
     
     
       24. The electronic system of  claim 23  wherein the wireless communication network is one of a Code Division Multiple Access (CDMA) network, a Wideband Code Division Multiple Access (WCDMA) network, a Global System for Mobile Communications (GSM) network, an Advanced Mobile Phone System (AMPS) network, a Time Division Multiple Access (TDMA) network, a General Packet Radio Service (GPRS) network, an Enhanced Data rates for GSM Evolution (EDGE) network, a Personal Digital Cellular (PDC) network, and a Universal Mobile Telecommunication System (UMTS) network. 
     
     
       25. The electronic system of  claim 23  wherein the wireless communication network is a wireless local area network. 
     
     
       26. An amplifier having a frequency band of interest associated therewith, the amplifier comprising a frequency selective network, an amplification stage, and feedback circuitry in a first feedback loop, the frequency selective network being operable to provide noise shaping in the frequency band of interest using negative feedback via the feedback circuitry, the amplification stage being operable to open the first feedback loop during operation of the amplifier, the amplifier further comprising feed forward circuitry coupled to the first feedback loop and bypassing the amplification stage, the feed forward circuitry being operable to provide a second feedback loop when the first feedback loop is open thereby preserving amplifier loop stability. 
     
     
       27. The amplifier of  claim 26  wherein the frequency selective network comprises at least one resonator stage. 
     
     
       28. The amplifier of  claim 26  wherein the frequency selective network comprises at least one integrator stage. 
     
     
       29. The amplifier of  claim 26  further comprising bias control circuitry for controlling a bias point associated with the amplification stage. 
     
     
       30. The amplifier of  claim 29  wherein the bias control circuitry comprises bias voltage control circuitry for controlling a bias voltage associated with the amplification stage, and bias current control circuitry for controlling a bias current associated with the amplification stage. 
     
     
       31. The amplifier of  claim 30  wherein the bias voltage control circuitry is operable to set the bias voltage at one of a plurality of bias voltage values, and wherein the bias current control circuitry is operable to set the bias current at one of a plurality of bias current values. 
     
     
       32. The amplifier of  claim 29  wherein the bias control circuitry is operable to control the bias point in response to any of an input signal level, power control information received from a remote device, and battery charge information. 
     
     
       33. The amplifier of  claim 26  wherein the amplification stage comprises a single transistor and an inductor which are operable to alternately conduct load current. 
     
     
       34. The amplifier of  claim 26  wherein the amplification stage at least one switching device. 
     
     
       35. The amplifier of  claim 34  wherein the at least one switching device comprises any of a field-effect transistor, a bipolar junction transistor, and a vacuum tube. 
     
     
       36. The amplifier of  claim 26  wherein the amplification stage is characterized by operation in one of classes B, AB, C, D, E, F, G, and H. 
     
     
       37. The amplifier of  claim 26  wherein the frequency band of interest is the radio frequency (RF) band. 
     
     
       38. The amplifier of  claim 26  wherein the frequency band of interest is the base band. 
     
     
       39. The amplifier of  claim 26  wherein the feedback circuitry comprises a plurality of passive circuit components. 
     
     
       40. The amplifier of  claim 26  wherein the feedback circuitry comprises a combination of active and passive components. 
     
     
       41. The amplifier of  claim 26  wherein the feed forward circuitry comprises at least one passive circuit component. 
     
     
       42. The amplifier of  claim 26  wherein the feed forward circuitry comprises at least one active component. 
     
     
       43. The amplifier of  claim 42  wherein the at least one active component comprises a common-emitter transistor coupled between an output and an input of the amplification stage. 
     
     
       44. An electronic system comprising the amplifier of  claim 26 . 
     
     
       45. The electronic system of  claim 43  wherein the electronic system comprises one of a mobile wireless communication device and a wireless base station in a wireless communication network. 
     
     
       46. The electronic system of  claim 45  wherein the wireless communication network is one of a Code Division Multiple Access (CDMA) network, a Wideband Code Division Multiple Access (WCDMA) network, a Global System for Mobile Communications (GSM) network, an Advanced Mobile Phone System (AMPS) network, a Time Division Multiple Access (TDMA) network, a General Packet Radio Service (GPRS) network, an Enhanced Data rates for GSM Evolution (EDGE) network, a Personal Digital Cellular (PDC) network, and a Universal Mobile Telecommunication System (UMTS) network. 
     
     
       47. The electronic system of  claim 45  wherein the wireless communication network is a wireless local area network. 
     
     
       48. A radio frequency (RF) amplifier having a frequency band of interest associated therewith, the RF amplifier comprising a frequency selective network, an amplification stage, and feedback circuitry in a first feedback loop, the frequency selective network including at least one resonator for providing noise shaping in the frequency band of interest using negative feedback via the feedback circuitry, the amplification stage comprising a switch and an inductor which are operable to alternately conduct load current, the switch being operable to open the first feedback loop while the inductor is conducting the load current, the RF amplifier further comprising feed forward circuitry coupled to the first feedback loop and bypassing the amplification stage, the feed forward circuitry being operable to provide a second feedback loop when the first feedback loop is open thereby preserving amplifier loop stability. 
     
     
       49. The amplifier of  claim 48  further comprising bias control circuitry for controlling a bias point associated with the amplification stage. 
     
     
       50. The amplifier of  claim 49  wherein the bias control circuitry comprises bias voltage control circuitry for controlling a bias voltage associated with the amplification stage, and bias current control circuitry for controlling a bias current associated with the amplification stage. 
     
     
       51. The amplifier of  claim 50  wherein the bias voltage control circuitry is operable to set the bias voltage at one of a plurality of bias voltage values, and wherein the bias current control circuitry is operable to set the bias current at one of a plurality of bias current values. 
     
     
       52. The amplifier of  claim 49  wherein the bias control circuitry is operable to control the bias point in response to any of an input signal level, power control information received from a remote device, and battery charge information. 
     
     
       53. The amplifier of  claim 48  wherein the switch comprises either of a field-effect transistor and a bipolar junction transistor. 
     
     
       54. The amplifier of  claim 48  wherein the amplification stage is characterized by operation in class AB. 
     
     
       55. The amplifier of  claim 48  wherein the feedback circuitry comprises a plurality of passive circuit components. 
     
     
       56. The amplifier of  claim 48  wherein the feedback circuitry comprises a combination of active and passive components. 
     
     
       57. The amplifier of  claim 48  wherein the feed forward circuitry comprises at least one passive circuit component. 
     
     
       58. The amplifier of  claim 48  wherein the feed forward circuitry comprises at least one active component. 
     
     
       59. The amplifier of  claim 58  wherein the at least one active component comprises a common-emitter transistor coupled between an output and an input of the amplification stage. 
     
     
       60. An electronic system comprising the amplifier of  claim 48 . 
     
     
       61. The electronic system of  claim 60  wherein the electronic system comprises one of a mobile wireless communication device and a wireless base station in a wireless communication network. 
     
     
       62. The electronic system of  claim 61  wherein the wireless communication network is one of a Code Division Multiple Access (CDMA) network, a Wideband Code Division Multiple Access (WCDMA) network, a Global System for Mobile Communications (GSM) network, an Advanced Mobile Phone System (AMPS) network, a Time Division Multiple Access (TDMA) network, a General Packet Radio Service (GPRS) network, an Enhanced Data rates for GSM Evolution (EDGE) network, a Personal Digital Cellular (PDC) network, and a Universal Mobile Telecommunication System (UMTS) network.